The invention relates to rotating couplers for transmitting high frequency energy from a stationary to a rotating system and vice-versa. Such rotating couplers maybe of a wiping contact type or a non-contact type via transformer devices, which transform an apparent short-circuit at an air gap. The invention relates to such a non-contact rotating coupler.
The invention seeks to produce a non-contact rotating coupler with a large free inner passage suitable for transmitting several channels within a frequency range preferably larger than 500 MHz and at the same time providing; a small reflection coefficient, small variation of the reflection coefficient over the rotating range of 360.degree., small transit loss over the rotating range, small variation of the phase angle of the transmitted signal over the transit range, high attenuation of inductive distrubance between several rotating couplings, large band width of the transmission range, small dimensions, in particular small length in axial direction and small radial dimensions with a large free inner diameter.
According to the invention there is provided a rotating coupler based on the principle of the .lambda./2 resonant circuit for forming a multiple rotating coupler with a free inner space to allow the passing through of connection leads characterized in that the resonant spaces of the resonant circuit are folded. A compact construction is achieved by folding the conductor sections, which may be done in axial as well as in radial direction. The term "folding" is used herein to indicate the appearance of the section not its manner of production. Both the stationary and the rotary portions of the rotating coupler are equipped with a resonant structure, preferably a .lambda./4 resonator, whereby coupling of the resonators on both sides is effected conductively or directly for preference. Coupling of the two resonant circuits is conveniently effected by a capacitive load applied at the high-ohmic point.
According to the invention each rotating coupler may be designed as a structural modular unit. Due to the modular design it is possible to link as many rotating couplings in axial direction by screw or even flange connections as is necessary for a particular application.
In order to achieve good access to the coaxial feeders or leads in the form of coaxial cables from outside the coupler as well as from inside the coupler, the excitation from the stationary or the rotatable system is not related, as has been usual in the past, to the inner conductor, but to the outer conductor. This latter measure has the great advantage that there is a distance of approx. .lambda./2 between the coupling points, giving an extended transmission lead and thereby resulting in an attenuation of the unavoidable field interference at the coupling points to such an extent that the dependance of the electrical values upon the rotating angle of the rotating coupler becomes very negligible. This arrangement also makes it possible to build rotating couplers with an overall length of not more than approximately .lambda./2 --an advantage not possible with the previous designs --for a simple arrangement of the .lambda./4 transformer stages necessary for achieving a non-contact transition at the rotating point.